A Study of Glass Transition of Polymeric Materials by Specific Heat Spectroscopy

1. 采用本实验室自行搭建的交流量热实验系统。用FFT分析仪代替了系统中的锁相放大器，缩短了测量时间。传统的交流量热系统采用带孔的旋转板作为光调制器，对样品进行周期性加热。在这个项目中，两个偏振片，其中一个是旋转的，另一个是固定的作为光调制器，获得正弦光强。使用步进电机后，加热频率变得更加精确。对控制整个实验系统的个人计算机程序进行了修改，以适应FFT分析仪和步进砂浆控制器。利用该程序，可以实现连续改变加热频率的测量。对聚苯乙烯（MW=2000）进行了初步测定。测量时间不到传统锁相放大器测量时间的十分之一。实现了缩短测量时间的主要目标。这种新的实验系统将推动对高分子材料性能具有重要意义的热史研究。加热频率目前限定在0.5Hz ~ 30Hz范围内。扩大频率范围是未来的问题。

1. An experimental system of AC calorimetry constructed in our laboratory was used. The lock-in amplifier used in the system was replaced with FFT analizer to make measuring time shorter.2. Conventional AC calorimetry system uses a rotating plate with holes as the light modulator for periodic heating of the sample. In this project two polarizing plates, one of which is rotated and the other is fixed, were employed as the light modulator to obtain sinusoidal light intensity. The heating frequency became much more accurate by using a stepping motor.3. The program of the personal computer to control the whole experimental system was changed to fit the FFT analyzer and the stepping mortar controller. Using the new program we can make measurement changing the heating frequency successively.4. Preliminary measurement was made for Polystylen (MW=2000). The measuring time was less than one tenth of the measuring time of the conventional method using a lock-in amplifier. The main object of this project to make the measuring time shorter was carried out. Study of the thermal history which is important for the properties of polymeric materials will be progressed by this new experimental system.5. The heating frequency is limited in the range of 0.5Hz to 30Hz at present. To expand the frequency range is left as a future problem.